Calling appliance for telephone-switchboards.



Patented July l6, l90l.

r n. McBERT Y, CALLING APPLIANCE FOR TELEPHONE SWIT'CHBOARDS.

(Application filed mm 17, 1898.) (Ila Model.) 2 Shuts-Sheet l.

Witnesses; Inventor:

. f $30: 815m I R E by his Aw.-

PETER$ 00-, PNOTO-LITN Q. WASHINGTON I! C THE yonms No. 678,369. Ptantedluly l6, I90l.

F. n. NcBEBTY. CALLING APPLIANCE FOR TELEPHONE SWITCHBOABDS.

(Application filed June 1-1, was. A (No Ilodol.) I 2 Sheets-Shoot 2.

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Witnesses; Inventor-z Wawwsm. W Wm% UNITED STATES PATENT OFFICES.

FRANK R. MCBERTY, OF DOWNERS GROVE, ILLINOIS, ASSIGNOR TO THE WESTERNELECTRIC COMPANY, OF CHICAGO, ILLINOIS.

CALLING APIPLIAINCE FOR'TELEPHONE-SWITCH'BOARDS.

SPECIFICATION forming m or Lttersflatent No. 678,369, dated July 1 e, 1901'.

Application filed June 17, 1898. Serial No. ($8,737. on model.)

To allwhom it may concern:

Be it known that I, FRANK R. MOBERTY, a citizen of the United States,residing at Downers Grove, in the county of Dnpage and State ofIllinois, have invented a certain new and useful Improvement in CallingAppliances for Telephone-Switchboards,(CaseNo. 62,) of which thefollowing is a full clear, concise, and exact description.

This invention concerns the automatic apline and to discontinue thecalling-current when the called subscriber answers; to disconnect theoperators telephone from the plug-circuit When connection is made withthe line, the telephonehaving been normally in connection With the linefor testing purposes; to associate with the line a supervisory. signalresponsive to currents in the line dc termined by the position of thetelephone at the substation, but toefiace this signal dur ing thetransmission of calling-current, permitting its free operation only in asubsequent stage of the connection, and to associate the variousagencies for accomplishing these ends with the circuits and appliancesof a certain well-known type of switchboard.

Prior to this invention various appliances have been constructed forautomatically ringing the bell at a subscribers station, the applicationof the calling-current being determined by the act of making connectionwith the line and its cessation being caused auto matically in thecalled subscribers response to the call. Such appliances have commonlyinvolved mechanical means for determining the duration of current,together with me chanical catches and equivalent devices controlled bymagnets for disconnecting the source of calling-current.

The present invention aims to eliminate all mechanical interlockingmechanism, deterhelix controlled by current in the line determined .by achange in the resistance of the line, and a switch actuated by thislast-mentioned helix for disconnecting the source of calling-current. Itfurther consists in the combination, with the elements before mentioned, of a local circuitcontrolled by the said second helix adapted tomaintain the excitement of the helix independently of current in theline.

It also contemplates the combination of the electromagnetic helix withthe local circuits of the so-called relay-switchboard, hereinafter to bedescribed; circuits of the operators telephone broken throughtheinstrumentality @of the first-mentioned magnetic helix; means forbringing the supervisory signal into temporary association with theline, said means being controlled-by the second-mentionedelectromagnetic helix, and various other details of apparatus andcircuits, which will be fully set forth The type of switchboardhereinbefore referred to to which this invention is especiallyapplicable comprises a relay for each line and a secondary line-signalcontrolled thereby, a cut-0E relay for each line adapted to sever thenormal line connections with the relay, and a local circuit closed inmaking connection with the line to excite the cut-0E relay,

a supervisory signal in the local circuit associated with the plug usedin making'connection with the line, and a relay responsive to currentsin the line determined in the use of the telephone controlling thedisplay of the supervisory signal. In applying my invention in aswitchboard of this type I construct the electromagnet for applying thecallingcurrent to the line of comparatively high resistance andinter-pose it in the circuit with the supervisory lamp and the cut-offrelay.

I make the magnet for disconnecting the call I ing-current of lowresistance and include it in a shunt-circuit of the supervisory lamp andthe other magnet controlled by the supervisory relay responsive tocurrents in the telephone-line, and I furnish a local circuit closedthrough the agency of the last-mentioned electromagnet of the callingappliance to shunt the other electromagnet through itself. The telephonenormally connected with the line is disconnected by switch-contactscontrolled by the magnet which applies the calling-current, and a normalbreak in the plug-circuit for preventing the flow of calling-currentover the calling-line is completed by the electroinagnet, which cuts offthe calling-current. Hence in the operation of this appliance theestablishment of connection to a line cuts off the line-relay, appliescalling-current to the line, and disconnects the operators telephonetherefrom, the supervisory signal being rendered inert through theresistance of the electromagnet in series with it, while the removal ofthe telephone for use at the called station disconnects thecalling-current, closes the normal break in the plug-circuit, and bringsthe auxiliary supervisory signal under control of the supervisory relayby cutting out the resistance of the said magnet in circuit with thesignal. After the response of the called party subsequent changes ofline resistance are ineffective to break the plugcircuit, to cause theapplication of callingcurrent to the line, or to introduce resistanceinto the line-circuit of the supervisory signal. In addition to theabove-mentioned appliances I provide a commutator for determining theintermittent application of calling-current to the line and forconnecting a source of constant current not adapted for operating thesubstation-bell with the line in the intermissions of calling-current,so that the response of the called subscriber will instantly place theplug-circuit in condition to permit conversation.

This invention is especially useful in-connection with incomingtrunk-lines in central offices, inasmuch as the operator makingconnection therewith is under no necessity of communicating with asubscriber or doing other work involving the prolonged use of hertelephone in connection with the line, her sole duty being to test theline called for, to make connection with it, and to transmit acall-signal to the station. Hence the use of this automatic calling andtelephone-controlling apparatus onincoming trunk-lines avoids themanipulation of all keys and similar appliances, reducing the actsrequired on the part of the operator to testing the line called for andinserting the plug into the springjack thereof when the line is free forconnection.

The invention is illustrated in the attached drawings in associationwith a switchboard of the type hereinbefore mentioned.

Figure 1 of the drawings is a diagram representing the circuits and theelements of the apparatus involved in a telephone-switchboard. Thisdrawing shows the incoming terminal of a telephone trunk-line, togetherwith the call wire whereby the incoming trunk-operator commonly receivesher orders from distant exchanges, a single telephone line being shownterminating in the usual apparatus of the switchboard. Fig. 2 is anelevation of the appliance for controlling the connection with thetrunk-line circuit of the source of calling-current and of the telephoneand for determining the operation of the supervisory signal. Fig. 3 is aplan of the same device. Fig. 4 is an elevation of the opposite side.Figs. 5 and 6 are sectional views of the calling appliance on lines 5 5and 6 6, respectively, of Fig. 2.

Referring to the diagram Fig. 1, conductors 1 and 2 are the wires of anincoming trunkline from a different oliice of an exchange system. Thistrunk-line terminates, in effect, in a plug. This plug and theappliances associated with it, to be presently described, are locatedwith others in an incoming trunkline switchboard, as is well understoodby those familiar with telephony. All subscribers lines centering in theoffice which this trunk-line enters appear in spring-jacks in theincoming trunk-switchboard or are made accessible to the incoming trunkoperator by any other suitable means. In the drawings the singlesubstation-line shown is represented as provided with a spring-jack inthe incoming trunk-switchboard and with another spring-jack and withsuitable calling apparatus in a different switchboard in the sameoffice.

The substation is furnished with suitable telephonic and callingapparatus, comprising a receiving-telephone a, a transmitting-telephonect', a polarized call-bell a a condenser a and a telephone-switch a. Thecall-bell and the condenser are connected in a perinanently-closedbridge of the line-cireuit,which is, however, open as respectscontinuous currents, while the telephones are located in a normally openbridge, which becomes closed when the telephone is removed from thetelephone-switch. The line conductors 3 4 from this station are led fromthese appliances to aspring-jack Z) in the incoming trunk-switchboardand to a spring-jack Z) in another switchboard, which may be onearranged for the establishment of local or office connections. Each lineconductor is connected in multiple with a line-contact of each of thesespring-jacks. Extensions of the line condoctors are led to the poles ofa battery 0 and to earth, respectively, the winding of asignal-controlling relay (1 being interposed in conductor 3. This relayis adapted to complete a local circuit 5 6, including a secondaryline-signal e, together with a source of current. The signal econstitutes the subscribers means of calling for a connection and may beassociated with the spring-jack b in the switchboard. The lineconductors 3 and 4 also traverse the switch-contacts of the cut-E relayf, which is adapted to break the normal extensions of the line to earthand to battery when the magnet of the cut-off relay is excited. Themagnet of this relay is connected in a grounded conductor 7, which leadsto terminal contact-rings of all springjacks b and b of the line. Thiscircuit is designed to cooperate with another, presently to bedescribed, which becomes completed when connection is made with theline, so

- that the normal earth connections of the line are broken during theuse of the'line for conversation.

The terminal plug 9 of the incoming trunkline is adapted for insertioninto the springjack Z) and comprises three contact-pieces g, 9 and g forregistering with the two line contactsand the local contact-ring of thejack. The line-contacts g and g form the terminals of the wires 1 and 2,respectively, of the trunk-line. A conductor 8 forms apermanently-closed bridge of the trunk-line. This conductor includes asource it of current for supplying the substation-transmitter of a linewith which the trunk-line may be brought into connection and foroperating signals associated with the trunk-line, together withimpedance-coils, which serve to prevent the shunting of telephoniccurrents through the bridge. Conductor 2, leading to the contact-ring gof the plug, includes the magnet-winding of a relay '5 for controlling asupervisory signal j, associated with plug 9 in the switchboard. Theinstrumentalites through which the relayt' controls the display ofsignal j will be hereinafter described. Other circuit connections of thetrunk-line also exist with an appliance which I shall designate thecalling appliance, although its function comprises not only that ofsignaling the called station, but of disconnecting the testing apparatusand of controlling a signal. This appliance is represented in Figs. 2,3, and 4 and will now be described.

Two magnets and'l are provided, with their cores arranged coaxially.Each magnet is furnished with inwardly-bent pole-pieces 70' k and Z Zrespectively, the pole-pieces k and Z being secured together. Eachmagnet is provided with an armature lying between the inwardly extendingends of the polepieces and the spool of the magnet, fastened at one endto one of the pole-pieces and having its other end free and lying nearthe other pole-piece. Thus armature 70 of magnet 7c is secured topole-piece 7c by a thin flat strip of metal 10 which may be a flexibleribbon of iron about one thousandth of an inch thick. The

other extremity of armature 70 lie's facing the inner surface of thepole-piece 70 so that if the magnet be excited the armature will bedrawn up into contact with the pole-piece, completing the magneticcircuit of the core. Similarly armature Z of magnet l is secured at oneend to pole-piece l and has its other extremity in position to beattracted to pole-piece Z The pole-piece Z carries four switch-springs mm and n 72', these springs being rigidly secured between blocks ofinsulating material fastened to the pole-piece Z and extending parallelwith the axis of the magnets. The'free extremities of springs and n restnormally on studs n 41 of insulating material, which project from theouter face of pole-piece Z Spring m rests similarly on another stud mprojecting from the pole-piece, while spring m rests on a contact-anvilm secured to the pole-piece, but insulated therefrom. Spring 71. carriesa contact-piece 72 which is adapted to impinge upon spring m when springat is lifted. Beneath this contact-piece n the armature Z carries aprojecting pin Z, of insulating material, which is thrust against thespringn to raise it and force i t upward against spring m when thearmature is raised. Near its other edge, beneath the spring a, thearmature Z carries a contact-stud l, which is adapted to strike and makecontact with spring n when the armature is raised and to thrust thelatter against an insulating-pin m to lift spring m from itsresting-anvil. The pole-piece it of magnet is likewise carries twoswitch springs o and o, insulated from it. The free extremities of thesesprings extend forward beneath the extremities of springs m and m,respectively, and are adapted to strike and make contact with thesesprings,-

at the same time lifting them from their normal resting-places when thearmature 70 is attracted in the excitement of magnet 70. These springswhen at rest lie upon insulating-stops o o in the pole-piece k Normallysprings 71 and n rest on their insulating-stops n and 12 respectively,while springs'm and m rest on their stop at and contact m Springs 0 and0 rest on their stops 0 and 0 out of contact with springs m and m. Whenarmature 79 is raised through the excitement of its magnet, itscontactpieces are thrust against springs m and m, respectively, raisingspring m from its stop 'm and spring m from its anvil m When nowarmature Z is raised, the insulating-pin Z strikes the spring 12,raising it from its stop 91 and thrusting the contact it against thespring m, thereby raising the latter spring away from the contact-spring0, while the contact-stud Z is thrust against spring 72, makingelectrical connection with it, forcing itagainst the stud m and thusraising the spring m from the contact-spring o.

The calling appliance is located in any suitable position in theswitchboard. Spring m of this appliance is connected by wire 9 withconductor 1. Conductor 2 of the trunk-line circuit is severed, theincoming end of the wire being connected with contact-spring n and thewire leading through the supervisory relay to the contact-piece g of theplug being connected with the contact-sprin g m. Spring 0 is connectedwith earth. Spring 0 is con;- nected with a brush or contact-pieceresting on a constantly-rotating commutator p, having two segments, oneof which, 1), forms about one-fourth of the periphery, and the other ofwhich, 19 forms nearly the remaining three-fourths. The segment 1)constitutes one terminal of a generator 13 of alternatingcalling-current, the other terminal of the generator being grounded. Thesegment 132 forms one terminal of a grounded battery of electromotiveforce substantially equal to that of battery It. The commutator may bearranged to rotate once in twelve seconds. Hence this device will applythe generator 13 and the battery alternately to the spring 0, theduration of the connection of the callinggenerator being three secondsand that of the source of steady current nine secdnds in each period.

The operator is provided with the usual telephone q for testing purposesand for receiving orders over an order wire 10. A branch 11 from thistelephone, whose circuit is grounded, is led to the contact-anvil m Thecontact-piece g of the plug forms the terminal of a group of conductorsleading from the free pole of a grounded battery 1, which are involvedin the operation of the cut-01f relay, the supervisory signal, and thecalling appliance. One terminal of magnet is connected by wire 12 withthe free pole of battery 1", and one terminal of magnet Z is likewiseconnected by wire 13 with the same battery. The other terminal of magnet70 is connected by wire 14 with signal-lampj, from which the circuit isled by wire 15 to contact 9 of the plug. The other terminal of magnet Zis connected by wire 16 with the armature t of relay 1' and also by wire17 with the armature Z of magnet Z. Contact n is connected by wire 18with wire let from magnet 70. The contact-anvil t of relay 1 is unitedby wire 19 with wire 15, leading to the contact-piece 9 The battery 0'may have an electromotive force often volts, then the cut-0E relayf mayhave a resistance of twenty ohms, the signallamp 2 should requiretwo-tenths of an ampere at four volts electromotive force, and themagnet k should be of thirty ohms and magnet Z of six ohms.

The mode of calling the central ofiice to obtain a connection with thecorrespondent line will be readily apparent, but may be briefly traced.The removal of the telephone from its switch for use at the stationpermits current to flow from the battery cat the central oflice throughthe relay 61 over the linewvires, returning to the battery 0 at thecentral office. This relay being excited closes the local circuit 5 6,leading to the secondary line-signal e, and thus signaling the call tothe operator. It is assumed that the connection is to be made at aswitchboard wherein the springjack 1) is located. This act of answeringthe call will be made with a plug and plug-circuit of well-knownconstruction having local circuit connections with the battery 1', whichapply a current to conductor 7 for exciting erases;

the cut-off relay and which involve suitable supervisory signalsassociated with the plug and plug-circuit. The excitement of the cutofirelay f breaks the normal extensions of the line conductors 3 and 4: tothe battery h and to earth, respectively, and leaves the line connectedwith the plug-circuit.

Obviously the mechanism forming the subject of this invention concernsincoming calls, however, or connections to be made to the line tostation A, whether by means of a plugcircuit terminating in a plug g andwholly located within the same office or by means of a trunk-linecircuit from a different office. It will be apparent that the conductors1 and 2 might extend to an answering-plug at the switchboard whereon thespring-jack b is located, in which case the insertion of plug 9 into aspring-jack of a line to be called would signal the called partyautomatically, the functions of the calling appliance being exercised inthe same way as in connection with a trunk-line; but inasmuch as anoperator engaged in answering calls is required to perform variousspecial acts and to hold conversation with subscribers in the process ofmaking connection the automatic ringing appliance is of greateradvantage in connection with incoming trunk-lines in the manipulation ofwhich the incoming trunk operator is not called upon to perform any actsout of the regular routine of few motions. Hence the invention has beenshown and will be described in connection with incoming trunk-lines,although it will be understood that the contrivance is applicable to anycalling-plug.

An operator at a distant office to which trunk-line 1 2 extends havingreceived a call for connection with the station A of the office hereindescribed brings her transmitting-telephone into connection withorder-wire 10 and, addressing the operator listening at telephone q,instructs her to make connection with line to station A by means oftrunk-line 1 2. Of course any of the well-known modes of selecting ordesignating the trunk-line to be used may be employed. The operatortaking the plug 9 applies the tip g of the plug to the contact-ring ofspring-jack b of the line called for in the switchboard hereindescribed. This act connects her grounded telephone q with thecontact-ring through conductors 1 9 11, the contact-spring m being atrest on its anvil m If the line were in use a battery 0' would beconnected with the contact-ring of some spring-jack, so that a currentwould flow through the telephone of the operator making the test at eachapplication of the testing-plug to the jack. Finding the line free forconnection the operator inserts plug 9 into the spring-jack b. This actbrings the contact g into registration with the contact-ring ofspring-jack b and completes a local circuit of battery 1 as follows:from the free pole of the battery through wires 12, 14:, 15, and 7,including the magnet 70, lamp-signal j, and cut-oft relay f. The our-TIO . the magnets 70 and f. The excitement of the cut-off relay f'breaksthe normal earth connections of the line. The magnetization of magnet Itbrings the springs 0 and 0 into contact with the springsm and m,respectively, at the same time breaking contact between the anvil m andspring m, whereby the operators telephone is disconnected from theplug-circuit and the calling-current is applied to it. Conductor 1 ofthe plug-circuit is grounded and conductor 2 is brought into connectionwith the commutator 19 through the agency of spring 0. In the rotationof the commutator the battery and the generator are alternately appliedto the conductor 2. Obviously each application of the generator 19 willring the substation-bell a The current from this generator,being greatlyimpeded by the condenser and the bell a at the substation, will beinsuflicient to excite the relay c. When the telephone at the station isremoved from its switch in response to the call, a path of lowresistance is created at the substation. Current will flow from eitherthe battery or the generator 11 through the low-resistance path thusproduced sufficient inquantity to excite the relay i and cause it toattract its armature t". The purpose of applying the battery to the linein the intervals of the application of calling-current is twofold:first, that the disconnection of the calling apparatus and thecompletion of the plug-circuit may instantly follow the taking of thetelephone at the substation, whatever he the position of commutator 19,and, second,

that the excitement of relay inlay be insured by the passage of a steadycurrent rather than to be dependent on current of alternating character,such as the calling-current. The attraction of armature i into contactwith its anvil i closes a branch of the local circuit through wires 13,16, and 19, including the magnet}. This magnet being excited thrusts thecontact n against the contact-spring 'm and raises contact-springs m andm from the springs 0 and 0', at the same time closing contact betweenarmature Z and contact-spring n. The conductor 2 of the plug-circuit isthus completed, the source of calling-current is disconnected from thecircuit, and the 10- cal circuits are shifted as follows: Oircuit isclosed through wires 13, 16, 17, and 18 in shunt of magnet and includingthe magnet l. Inasmuch as this circuit is independent of the contacts4." and t the magnet Z is no longer controlled by the supervisory relayi. and will remain excited as long as the local circuit 12, 13, 16, 17,18, 14, 15, 7 remains closed-that is, while the connection remains. Theresistance in circuit with the lampj is greatly reduced through theshunting of magnet k by magnet I, so that the current through thesignal-lamp may be sufficient to light .the lamp. It'will be noted,however, that this lampis now subject to the control of suhighresistancein its circuit.

pervisory relay 2', inasmuch as the'supervisory relay closes ashunt-circuit 19 16 about the lamp when it is excited. While the callingappliance was in operation the signal-lamp j remained dark on account ofthe Thus confusion of the operator by meaningless signals is avoided.After the response of the called party, and the disconnection of thecalling-j current the supervisory signal becomes effective and iscontrolled by the relay 71 in re sponse to the operation of thetelephoneswitch at the substation in the usual way. When at thetermination of conversation the telephone is replaced on its switch, therelay 1' is deprived of current, the shunt about the signal-lamp isbroken, and the lamp becomes lighted. Its illumination may serve as asignal for disconnection, to be followed by the withdrawal of plug 9from spring-jack b. When the plug is thus withdrawn, themagnets Z and 7care deprived of current and the calling appliance is returned to itsnormal condition. v

My invention is defined in the following claims:

1. The combination with a telephone-line extending from a substation toa central offlce, and a switch at the substation of the line fordetermining the flow of current therein, a magnet responsive to currentin the line, a source of calling-current and means for applying the sameto the line, an electromagnetic switch controlled through the agency ofthe switch at the substation, for disconnecting the source ofcalling-current from the line, a supervisory signal adapted to be c '0ntrolled by the first-mentioned magnet, circuit connections rendering thesignal unresponsive to said magnet, and means controlled by saidelectromagnetic switch for changing said circuit connections andbringing the supervisory signal under the control of said magnet,substantially as set forth.

2. The combination with a telephone-line extending from a substation toa central office, and a switch at the substation, actuated in the use ofthe telephone,-fo r determining the flow of current in the line, asource of calling current and means for applying the same to the line, asource of direct current, an electromagnetic switch adapted todisconnect the said source of calling-current and connect the source ofdirect current, a relay responsive to current in the line, and a localcircuit controlled by said relay including said electromagnetic switch,whereby said electromagnetic switch is operated when thesubstationtelephone is brought into use, as set forth.

3. The combination with a telephone-line extending from a substation toa central office, a, switch at the substation, actuated in the use ofthe telephone, for controlling the ci'rcuit of the line, means at thecentral office for making connection with theline, asource of current, arelay responsive to the flow of current in the line, a source ofcalling-current and an electromagnetic switch adapted to connect saidsource of calling-current with the line, a local circuit closed inmaking connection with the line to operate said electromagnetic switch,a second electromagnetic switch adapted to disconnect thecalling-current from the line, a local circuit controlled by said relayfor operating said last-mentioned switch, a supervisory signal adaptedto be controlled by said relay, circuit connections normally renderingsaid signal unresponsive to the relay, and means, controlled by thelast-mentioned switch, for bringing said supervisory signal under thecontrol of the relay, substantially as described.

4. The combination with a telephone-line, a line-signal therefor innormal circuit connection with the line, spring-jacks for makingconnection with the line, and a cut-0E relay for severing the normalcircuit to the signal in a portion of a local circuit terminating incontact-pieces of said spring-jacks adapted to register withcontact-pieces of a plug inserted in a jack, a source of callingcurrent,an electromagnetic switch for applying said source of calling-current tothe plug circuit, said electromagnetic switch being in a conductorterminating in said local contactpiece of the plug, and suitable meansfor disconnecting the source of calling current; whereby thecalling-current is applied and theline-signals are disconnected fromtheline when the plug is inserted in a spring-jack of the line, asdescribed.

5. The combination with a telephone-line having normal connections witha line-signal, means for making connection with the line comprisingspring-jacks of the line and a plug and plug-circuit, a cut-olf relayfor severing thenormal earth connections of the line and a local contactincluding the said cut-off relay comprising a conductor associated withthe line including the magnet of the relay and a part terminating inalocal contact-piece of the plug, a supervisory signal-lamp in theconductor terminating in said local contactpiece of the plug, a sourceof calling-current, an electromagnetic switch for applying the source ofcurrent to the telephone-line, circuit connections of the magnet of saidswitch with the local circuit adapted to prevent the lighting of thelamp, a supervisory relay for controlling the lamp, means foreliminating the magnet of the electromagnetic switch from the localcircuit of the lamp, as described; whereby the signal-lampis renderedineffective during the transmission ofcallingcurrent by theelectromagnetic switch in its circuit.

6. The combination with a telephone-line, a switch at the station forchanging the resistance of the line in the use of the telephone, asupervisory signal associated with the line, a relay responsive tocurrent in the line controlling said signal, a source of calling-currentand a switch for applying the said source of current to the line tocall, circuit nections, whereby the signal-lamp is rendered ineffectiveduring the transmission of a call, as described.

7. The combination with a telephone-line and a switch for changing theresistance of the line in response to a call, a source of call-.

ing-current and means for applyingit to the 1ine,'a supervisory signalnormally responsive to currents in the line, an electromagnetic switchadapted to disconnect the source of calling-current from the line, saidswitch being responsive to change of current in the line produced in theuse of the telephone, circuit connections of the supervisory signaladapted to interrupt the control of said sit!- nal by currents in theline, and an appliance associated with the said electromagnetic switchcontrolling the circuit connections, whereby the signal is renderedineffective during the sending of a call but is automatically renderedeffective when the call receives response, as described.

8. The combination with a telephone-line, a supervisory relay in theline responsive to currents therein determined in the use of thetelephone, a supervisory lamp-signal nor mally controlled thereby in alocal circuit closed in making connection with the line, a source ofcalling-current and an electromagnetic switch adapted to apply saidcalling-current to the line, the magnet of said switch being of highresistance and being located in series with the lamp-signal, anelectromagnet responsive to current in the line and a switch controlledthereby adapted to shunt the electromagnet of said electromagneticswitch, as described.

9. The combination with a telephone-line having a switch at itssubstation for determining the flow of current in the line in the use ofthe telephone, a relay responsive to currents in the line, a localcircuit associated with the line divided at one pointinto parallelbranches, completed in switch-contacts closed in making connection withthe line, a source of calling-current, an electromagnetic switch adaptedto apply said source of calling-current to the line, said switch havingits electromagnet in one branch of the said local circuit, a secondelectromagnetic switch adapted to break the connections of the saidsource of calling-current with the line, said switch being in the otherof the parallel branches, said second-mentioned branch be- 'ingcontrolled by the relay responsive to currents in the line, asdescribed.

10. The combination with a telephone-line and a switch at the stationthereof for determining the flow of current in the line in the use ofthe telephone, of a local circuit associated with the line in aswitchboard, and switch-contacts closed together in the act of makingconnection with the line to complete LII the said circuit, said circuitbeing divided into parallel branches, of a source of calling current, anelectromagnetic switch adapted to apply the said source of cu rrent tothe line,-

the magnet of said switch being in one of said branches, a secondelectromagnetic switch adapted to break the connection of said source ofcurrent with the line, said electromagnetic switch being in the other ofsaid branches, a supervisory signal in the first mentioned branch, arelay responsive to currents in the line having its switch-contacts inthe secondmentioned branch,and a switch actuated by the magnet in saidsecond-mentioned branch adapted to shunt the magnet of the switch insaid first-mentioned branch, as'described.

11. The combination with a telephone-line and a switch at the stationthereof for determining the flow of current in the line in the use ofthe telephone, of a local circuit associated with the line inaswitchboard, and switch-contacts closed together in the act of makingconnection with the line to complete the said circuit, said circuitbeing divided into parallel branches, of a source of callingcurrent, anelectromagnetic switch adapted to apply the said source of current tothe line, the magnet of said switch being in one of said branches, asecond electromagnetic switch adapted to break the connection of saidsource of current with the line, said electromagnetic switch being inthe other of said branches, a supervisory signal in the firstmentionedbranch, a relay responsive to currents in the line having itsswitch-contacts in the secondmentioned branch, and a switch actuated bythe magnet in said second-mentioned branch adapted to bring the magnetin said secondmentioned branch into parallel with a magnet in saidfirst-mentioned branch, the magnet in said second-mentioned branch beingof low resistance, substantially as described.

12. The combination with a telephone-line extending from a substation toa central of fice, and a switch at the substation, actuated in the useof the telephone, for changing the resistance of the line-circuit, of asource of calling-current and means for breaking the telephone linecircuit and connecting said source of calling-current with the endleading to the substation, a magnet in thelinecircuit traversed bycalling-current,said magnet being responsive to increased current in thecircuit, a switch operated by said magnet for disconnecting said sourceof calling-current and simultaneously completing the telephone-linecircuit, a source of steady current, and a continuously rotatingcommutator adapted to complete thecircuit of said source ofcalling-current intermittently and to substitute therefor said source ofsteady current in the intermissions, whereby a source of current isalways included in circuit with said magnet to excite the same when thecalled party responds, substantially as described.

13. The combination with a telephone-line having normal connectionsbetween its line conductors, a cut-01f relay controlling the said normalconnections, spring-jacks of the line and a local circuit terminating inlocal contact-pieces of. the jacks including the magnet of saidcut-oflt' relay, a plugand plug-circuit for making connection with theline, and a conductor adapted to cooperate with the said local conductorassociated withthe line terminatingia a contact-piece of the plugadapted to register with a contact-piece of the spring-jack in which theplngis inserted, said local circuit associated with the plug beingdivided into parallel branches; a relay in the plug-circuit responsiveto currents in the line determined in the use of the telephone, saidrelaycontrolling one of said branches, and a supervisory lamp-signal inthe other branch; a source of calling-current, an electromagnetic switchfor connecting the terminals of said source of current with theplug-circuit, the electromagnet of said switch being included in thebranch of the local circuit with the signal-lamp an electromagneticswitch adapted to break the connection of said source of calling-currentwith the line, the electromagnet of said switch being incl uded inthebranch of the local circuit controlled by the supervisory relay, andlocal circuit connections controlled by said second mentionedelectromagnetic switch adapted to bring the magnet thereof into shunt ofthe magnet of said first-mentioned switch, said magnet being of lowresistance, substantially as described. I

14'. In combination with a plug and plugcircuit a pair of switch-springsconnected with the different conductors of the plug-circuit, aresting-anvil for one of said springs forming the terminal of anoperators telephone for testing, switch-springs adapted to be thrustagainst the said springs to make contact with them and to raise one ofthe springs from the said contact-anvil, an electromagnet controllingsaid second-mentioned pair of springs, said magnet being in a localcircuit closed in the use of the plug as described; wherebycalling-current isapplied and the plug-circuit of the operatorstelephone is disconnected in using the plug, as described.

15. In a calling appliance for a plug-circuit the combination of twopairs of springs adapted to form electrical contact with each other, oneof said pairs of springs being'connected with the plug-circuit and theother with the terminals of a source of calling-current, of twoelectromagnets, one acting upon the terminal springs of said source ofcurrent to thrust them against the other springs,

and the other magnet adapted to act on said ing the calling-currentsuccessively, as described.

16. The combination in a calling appliance for association with theplug-circuit, of three springs normally out of contact with each other,two of said springs forming normallyseparated terminals of a plug in theplug-circuit, and the other spring forming the terminal of a source ofcalling-current, two magnets, one adapted to thrust said calling-springagainst one of said plug-circuit springs, and the other magnet adaptedto thrust one of said plug-circuit springs against the other, raisingthe latter from the calling-springs, and means for exciting the saidmagnets successively in the order of their description.

17. The combination in a calling appliance for association with theplug-circuit, of a pair of switch-springs connected with the terminalplug, a switch-spring beneath one of these connected with theplug-circuit but disconnected from the terminal plug, a pair ofswitchsprings forming the terminals of a source of calling-current, anelectromagnet adapted to thrust said calling-springs into contact withsaid springs connected with the plug-circuit, of an electromagnetadapted to thrust the springs connected with the like conductors of theplug-circuit into contact with each other, and simultaneously to raisethe springs connected with the plug-circuit from the callingsprings, andmeans for exciting the magnets successively in the order described.

18. In a calling appliance, the combination with switch-springs m and'nforming terminals of a break in one side of a plug-circuit, aswitch-spring m connected with the other side of the plug-circuit,calling-springs o and o, switch-spring n and contact Z therefor, anormal resting-anvil m for the spring m, of the 'magnet 7c for thrustingsprings 0 and 0 into contact with springs m and m, a magnet Z forthrusting spring n into contact with spring m, raising springs m and mfrom springs o and o and closing contacts Z 02, means for exciting themagnets successively, and a local circuit controlled in contacts 1 11including the magnet Z, as described.

19. The combination with a magnet and pole-pieces thereof projectingtoward each other, and an armature lying between the magnet and thepole-pieces, of the switchsprings n and m adapted to be raised andpressed into contact when the armature is attracted, and a restingcontact for the spring m, as described.

20. The combination with a plug and the plug-circuit thereof, of atesting appliance in normal connection with the plug-circuit, a

source of calling-current, an electromagnetic switch adapted to breakthe connection of said testing appliance and to make connection of saidsource of calling-current with the plug-circuit, and local circuitconnections of the said switch made operative in using the plug toexcite the switch, an electromagnet adapted to break the circuit of thesource of calling-current, and means controlled from the called stationfor operating said last-mentioned magnet, as described.

21. The combination with a trunk-line and the terminal plug thereof, asubscribers line and a spring-jack therefor, of an operators telephoneconnected with the trunk-line, a source of calling-current, anelectromagnetic switch adapted to break the circuit of the telephone andapply the source of callingcurrent to the line, and circuits madeoperative in registering contacts of the plug and jack to excite themagnet of said switch, an electromagnetic switch adapted to break thecircuit of the source of calling-current, and means actuated byincreased current in the line for operating said switch, as described.

22. The combination with a telephone-line and means for changing theresistance of the line in the use of the telephone, a spring-jack forthe line, a plug and plug-circuit for making connection with thespring-jack, a source of current and an electromagnetic switch forconnecting the source of current with the plug-circuit, and circuitconnections for exciting the actuating-magnet of said switch closed inregistering contacts of the plug and spring-jack, an electromagnet inthe path of current in the line, and a shunt of the actuating-magnet ofsaid electromagnetic switch controlled by said last-mentioned magnet;whereby the source of calling-current is applied to the line whenconnection is made with the line, but is disconnected therefrom in theuse of the telephone, as described.

In witness whereof I hereunto subscribe my name this 28th day of April,A. D. 1898.

FRANK R. MCBERTY.

lVitnesses:

ELLA EDLER, MYRTA F. GREEN.

